Currying - Part 6 of Functional Programming in JavaScript

hello what is currying currying is when a function doesn't take all of its arguments upfront instead it wants you to give it the first argument and then the function returns another function which you are supposed to call with the second argument which in turn will return a new function which you are supposed to call with the third argument and so on until all the arguments have been provided and then the function at the end of the chain will be the one that returns the value that you actually what does it sound confusing good the feeling of confusion is your friend it means you're learning before we get to it I'm going to incorporate some viewer feedback into the show this one is for you Joshua foreground and everything have a look at this beautiful function this function is not curried but we're going to curry it up in just a minute it's a very simple function it takes a name a size and element all strings and returns another string let me call it and run it fluffykins is a tiny dragon that breathes lightning let's clear all that proof here is the same function in the korean version dragon is a function that takes a name it will in turn return another function which takes size which in turn will return another function which takes an element which in turn will return the final strength I'm going to call it and log the output now remember dragon will take a name block Akins and it will return another function which takes a size tiny which in turn returns a third function which takes an element lightning let's run that again fluffykins is a tiny dragon that breathes slightly so you see that it's a chain of functions and if i just remove this last lightning call here and just run the code it would just show that oh it's a function the idea with carrying is that your function can pass through the application and gradually receive the arguments that it needs the function goes through your app you sprinkle it with some arguments here you spice it up with an argument here and here you add the final one and you get your output so for instance you might have broken out dragon here into fluffykins dragon and then refer to it here and you would get the same output or maybe into three parts tiny dragon and we run it again and we get the same result now our dragon function here is written from the start to be curable but every functional library worth its salt has a way of making nan Korea Bowl functions career proof now dragon is back in its standard form the one we saw from the beginning there is no currying here it's just the normal arguments as an example I'm gonna use lo - vs co MP I mean stole low - [Music] dippity-do in stock now we can use it in pour here we go and then we just do hungry just overwrite the existing one BAM and now fluffykins it's a tiny dragon that means I think you don't have to use slow - specifically for this all libraries with any kind of functional nature has a career option that's what currying is and how it works but why is it useful postproduction Leviosa so what you see here has no carrying at all it's just normal code we're gonna improve it a bit with carrying let's walk through it we have a dragons array we have a couple of lightning dragons here knew me and fluffykins but we also have a fire dragon and we also have our time warp dragon that's serious business we are going to get to line eight and nine but let's first look at line eleven and twelve where we filter out the dragon the lightning dragons from the Dragons array so we just call filter on dragons you all recognize this from the previous episodes filter takes a callback which will get every item and that item will be checked against this has element function if so it has element lightning and we pass in the object and we get a true or false and this will then be passed to lightning dragons just let me run that and you see that it's fluffykins and nume that is filtered off if you look at has element it's a function that takes an element this is this string here goes here and the filtered object or the iterated the object that filter iterates goods here and just compares that against the element property of the the object let's try to improve this with carrying let's import lodash and curry has element and then just remove this wrapping function just do that Wow so now has element is Korea ball that means when we call has element with lightning that means that it will return a new function which in turn expects we passed the the object to check if it has a limit lightning which allows us to pass it as the callback function to filter directly which is priestly call occlusion a curable function is simply a function that takes every argument by itself and then just returns a new function that expects the next dependency to the function until all dependencies have been fulfilled and the final value is returned so we call Carroll functions like this we call them with the first argument with the name which in turn will return a new function which we call with this size which in turn will return a new function which we call with the elements which will return the final value which we output here and it's Karl is a large dragon that breathes eyes and that is car people as usual I would love to hear from you either on Twitter at MP Jaime or in a comment down below either just write something nice or funny tell me what you think could be made better or tell me what you would like to see me make a video about speaking of which make sure that you don't miss the next episode make sure that you subscribe to the channel or follow me on Twitter until next Monday stay curious [Music]

Channel: Fun Fun Function

Views: 194,554

Rating: 4.9342647 out of 5

Keywords: Functional Programming (Programming Language Paradigm), JavaScript (Programming Language), Programming Language (Software Genre), Software Engineering (Industry), Software Engineer (Profession), Software Development (Industry), Software Developer (Project Role), Programmer (Profession), Programming (Musical Instrument), Programming Paradigm (Film Subject), Tutorial (Media Genre), Screencast (Software Genre), Currying

Id: iZLP4qOwY8I

Length: 8min 48sec (528 seconds)

Published: Mon Aug 17 2015

Reddit Comments

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I have been currying wrong this whole time. Here is how I use to do it, but your method is faster. https://www.youtube.com/watch?v=6OB8xs7lY48